Pregnancy video: 10 weeks

How your baby's growing

Though he's barely the size of a kumquat – a little over an inch or so long, crown to bottom – and weighs less than a quarter of an ounce, your baby has now completed the most critical portion of his development. This is the beginning of the so-called fetal period, a time when the tissues and organs in his body rapidly grow and mature.

He's swallowing fluid and kicking up a storm. Vital organs – including his kidneys, intestines, brain, and liver (now making red blood cells in place of the disappearing yolk sac) – are in place and starting to function, though they'll continue to develop throughout your pregnancy.

If you could take a peek inside your womb, you'd spot minute details, like tiny nails forming on fingers and toes (no more webbing) and peach-fuzz hair beginning to grow on tender skin.

In other developments: Your baby's limbs can bend now. His hands are flexed at the wrist and meet over his heart, and his feet may be long enough to meet in front of his body. The outline of his spine is clearly visible through translucent skin, and spinal nerves are beginning to stretch out from his spinal cord. Your baby's forehead temporarily bulges with his developing brain and sits very high on his head, which measures half the length of his body. From crown to rump, he's about 1 1/4 inches long. In the coming weeks, your baby will again double in size – to nearly 3 inches.

How your life's changing

At your next prenatal visit, you may be able to hear your baby's rapid heartbeat with the help of a Doppler, a handheld ultrasound device that your doctor or midwife places on your belly. The beating of your baby's tiny heart sounds like the thunder of galloping horses, and hearing it for the first time can be very moving.

Before you got pregnant, your uterus was the size of a small pear. By this week, it's as big as a grapefruit. You may or may not be ready for maternity wear now. Even if you're not there yet, your regular clothes are probably feeling uncomfortably tight and your breasts may be straining the seams of your bra. The thickening in your midsection is most likely due to slight weight gain and bloating. If you're between regular and maternity clothes, pants and skirts with forgiving elastic waistbands (or low-rise waistlines that sit below your belly) will provide some much-needed comfort.

Depending on your fitness level, you can most likely participate in a wide range of activities during pregnancy. Swimming and walking are excellent choices for the whole nine months. Exercise promotes muscle tone, strength, and endurance – three qualities that can help you carry the weight you gain during pregnancy, prepare you for the physical stress of labor, and make it easier to get back into shape after your baby is born. (Unfortunately, there's no evidence that regular exercise shortens labor.)

"My version of morning sickness developed every evening around dinnertime. I couldn't eat anything, but I was starving (and cranky) nonetheless. Things improved after I adjusted my schedule, eating my big meal in the morning and something light – usually crackers and cheese or cereal – for dinner."

Learn about: Infections during pregnancy

What do I need to know about urinary tract infections during pregnancy?

Urinary tract infections (UTIs) are the most common bacterial infection during pregnancy. Higher levels of progesterone are partly to blame. The hormone relaxes your urinary tract, which may slow the flow of urine, giving bacteria more time to grow. Later in pregnancy, other factors come into play as well.

An infection occurs when intestinal bacteria travel from your rectum to your urethra and make their way up your urinary tract, where they continue to multiply. Sometimes they cause a bladder infection called cystitis. Symptoms of cystitis include pain, discomfort, or burning when urinating, a more frequent urge to pee, and pelvic discomfort or lower abdominal pain. Your urine might look cloudy and have a foul smell.

It's important to see your caregiver if you think you have a bladder infection. Untreated cystitis can lead to a kidney infection that can make you seriously ill and increase your risk for preterm labor. If you do have cystitis, your practitioner will prescribe antibiotics that are safe during pregnancy to help prevent further problems. The antibiotics will likely relieve your symptoms within a few days, but remember to complete the entire course of treatment to destroy all of the bacteria.

Bacteria can also multiply in your urinary tract without causing any symptoms (a condition called asymptomatic bacteriuria), which is why your practitioner sent a sample of your urine to the lab at your first prenatal visit. You'll need to be treated with antibiotics if you have asymptomatic bacteriuria.

What do I need to know about bacterial vaginosis during pregnancy?

Bacterial vaginosis (BV) is a genital tract infection caused by an overgrowth of bacteria that usually live in small numbers in your vagina. You may not have symptoms with BV. If you do, you may notice a thin, milky white or gray discharge with a foul or fishy smell. (This odor is most apparent after sex.) You might also have some irritation or itching around your vagina and vulva, although at least half of all women with BV have no symptoms.

BV has been linked to an increased risk of preterm labor and preterm rupture of the amniotic membranes surrounding your baby. If you have symptoms of BV or if you're at risk for preterm labor, your caregiver will screen for the infection and treat you with antibiotics if the results are positive. If you're not at risk or don't have symptoms, your practitioner won't screen you.

What do I need to know about yeast infections during pregnancy?

Yeast infections are common vaginal infections that are even more likely when you're pregnant. They're caused by microscopic fungi in the Candida family. These fungi are found in the vaginas of nearly one-third of women and only become a problem when growth is so rapid that the yeast overwhelms other competing microorganisms. Your increased estrogen level during pregnancy causes your vagina to produce more glycogen, making it even easier for yeast to grow there. (Some researchers think estrogen also has a direct effect on yeast, causing it both to grow faster and to stick to the walls of the vagina better.)

A yeast infection won't hurt your developing baby. If you have an infection when you go into labor, there's some chance that your newborn will contract it as he passes through the birth canal. Yeast may cause a common infection called thrush, which is recognizable by white patches in a baby's mouth. Thrush isn't serious and is easily treated in healthy newborns.

Activity: Buy new bras and undies

It's probably time to upgrade your underthings. As your breasts and waistline grow and change, maternity bras and underwear can keep you comfortable. It's wise to shop for a maternity bra in an actual store (not online) so a sales associate can help you with sizing. Look for good support and room to expand. Your breasts might increase one or two more sizes over the coming months, especially if this is your first pregnancy.

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